Radial piston type hydraulic motor

ABSTRACT

A radial-piston type hydraulic motor having a cylinder housing with at least two rows of cylinder bores with pistons in each bore, the cylinder housing being provided with a central axially extending fluid flow and return passage and interconnected fluid passages communicating with the central passage and arranged to permit substantially simultaneous flow of fluid to and from the at least two rows of cylinder bores. A valve member provided in said central passage and axially movable is arranged to control the flow and return of fluid to the at least two rows of cylinder bores.

United States Patent inventor Arthur Frederick Allen Littleover, Derby,England Appl. No. 813,903

Filed Apr. 7, 1969 Patented Feb. 23, 1971 Assignee Rolls-Royce LimitedDerby, England Priority Apr. 5, 1968 Great Britain 1638 l/ 68 RADIALPISTON TYPE HYDRAULIC MOTOR 8 Claims, 4 Drawing Figs.

U.S. Cl 91/492,

91/180 lnt.Cl...., F0ll33/02 Field of Search 91/205,

204; 9l/l80, (cards); 103/161 (Cursory) [56] References Cited UNITEDSTATES PATENTS 1,488,528 4/1924 Cardini 91/180 2,303,685 12/1942 Eden etal..... 91/205 2,811,143 10/1957 Baines etal 91/180 2,989,005 6/1961Gardineer,.lr... 91/205 3,081,708 3/1963 Nyman et a1 91/205 PrimaryExaminer- Paul E. Maslousky Attorney-Cushman, Darby and CushmanABSTRACT: A radial-piston type hydraulic motor having a cylinder housingwith at least two rows of cylinder bores with pistons in each bore, thecylinder housing being provided with a central axially extending fluidflow and return passage and interconnected fluid passages communicatingwith the central passage and arranged to permit substantiallysimultaneous flow of fluid to and from the at least two rows of cylinderbores. A valve member provided in said central passage and axiallymovable is arranged to control the flow and return of fluid to the atleast two rows of cylinder bores.

PATENTEU FEB23 191:

SHEET 2 [IF 2 RADIAL PISTON TYPE HYDRAULIC MOTOR smaller total packagevolume may be achieved by using a suitable number of small ball pistonsin preference to a less number of large ball pistons.

The present invention relates to a construction of motor in which arelatively small size and weight for a motor power output can beachieved.

According to the present invention a radial piston type hydraulic motorcomprises a cylinder housing, two rows of cylinder bores in saidhousing, and interconnecting fluid passages adapted to permitsubstantially simultaneous flow of fluid to and from said two rows.

Preferably said rows comprise axially spaced rows of equiangularlyspaced apart bores, the bores of one row being angularly displaced withreference to the bores of the other row by half the angular spacing ofadjacent bores of each row. The axial spacing of the rows may be suchthat the bores of the two rows are at least partly interdigitated.

In this way the axial length of the motor may be considerably reduced.

There is preferably a central axially extending fluid flow and returnpassage, said interconnecting passages communicating with said centralpassage. In this case there is preferably a valve member axially movablein said central passage and adapted to control flow and return of fluidto said rows of bores.

The invention is particularly applicable to a motor in which there are aplurality of said pairs of rows, and control valve means adapted tobring a variably number of said pairs of rows into operation. Saidcontrol valve may well comprise said axial movable valve member.

The interconnected fluid passages may be formed integrally in saidhousing, or alternatively they may be formed in the outer surface of acylindrical insert which fits inside said housing.

The invention will now be particularly described merely by way ofexample with reference to the accompanying drawings in which:

FIG. 1 is an axial cross section through an hydraulic motor according tothe present invention.

FIG 2 is a view of the cylinder housing of the motor of FIG 1 taken inthe direction of arrow A,

FIG 3 is a transverse section on the line 3-3 of FIG 1, and

FIG 4 is a transverse section on the line 4-4 of FIG 1.

Referring first to FIG 1 an hydraulic motor comprises a cylinder housing10 of substantially annular form having formed therein six rows 11 to I6of cylinder bores 17, each row comprising six angularly spaced apartcylindrical bores disposed in the same transverse plane. In each ofthese bores 17 there is accommodated a tight fitting ball piston 18.

Concentrically surrounding the housing 10 there is an annular member 19rotatable with respect to the housing 10 and mounted therefrom inbearings 20. In this particular instance the housing 10 is stationarywhile the member 19 may rotate.

The member 19 carries on its inner periphery a series of cam tracks 21to 26, each of which cooperates with the ball pistons 18 of a respectiveone of the rows 11 to 16. The cam tracks are so shaped, as is best seenfrom FIGS. 3 and 4, that by forcing the ball pistons 18 to move radiallywithin their bores 17 in a particular pattern, rotation of the member 19may be effected.

High pressure fluid may be fed to and vented from the space within thebores 17 radially inward of the ball pistons 18 so as to enable the ballpistons to be forced out against, and allowed to retract from therespective cam track. In order to effect this supply and return, eachbore is connected by way of ducting to a central passage 27. Closelyfitting within this central passage there is an axially movable valvemember 28 which comprises an entrance hole 29 adapted to allow pressurefluid to flow from a feed port 30 in the housing 10 to a central bore 3]within the valve member and then to supply ports 32 and 33 which allowthe high pressure fluid to escape from the central bore 31 through thewall of the valve member. The outer surface of the valve member 28 isprovided with axially extending grooves one of which is shown at 34which connect with a fluid return-passage 35 in the housing 10.

The valve member 28 is splined at one extremity 40 to the member 19, andtherefore rotates with this member. The return grooves such as 34 andthe flow passages such as 32 and 33 are arranged alternately around theperiphery of the valve member 38 as can best be seen in sections ofFIGS. 3 and 4.

Each of the rows of bores 17 is provided with a series of passages topermit flow and return of pressure fluid as permitted by the valvemember 28. Thus the row 11 is provided with passages which are partlyvisible at 36 which interconnect each one of the bores 17 of this rowwith a corresponding bore of the next adjacent row 12. Thisinterconnection is indicated by arrows on FIG 2. Similarly the remainingpairs of rows 13 and l4: l5 and 16 are similarly interconnected.

Communicating with the interconnecting passages 36 there are a pluralityof feed parts or passages 37 which interconnect these passages withselected points on the periphery of the central channel 27. The ports 37are angularly spaced apart around the periphery of the channel 27. Itwill, therefore, be appreciated that because of the angular spacing ofthe flow and return passages in the valve member 28 and the angularspacing of the passages 37 which communicate with the spaces radiallyinwards of the ball pistons, it can be arranged that the ball pistonsare forced outwardly by the pressure fluid when they come adjacent aselected part of the respective cam track, and correspondingly the spacemay be vented so as to allow the pistons to retract when they areadjacent another selected part of the cam track.

Axial movement of the valve member 28 is sufficient to enable eitherone, two or three pairs of rows of pistons to be supplied withpressurized fluid. Thus it will be seen in FIG 1 that I by moving thevalve member slightly to the left, the extreme right-hand pair ofpistons will cease to be supplied with pressure fluid; by moving thevalve member to its extreme lefthand position only the extreme left-handpair of rows will be supplied with pressure fluid. In this way the motoris given in effect a variable gear box action in that when large torqueand low speed is required all the rows can be energized and as thetorque drops off and the speed increases the number of rows can becorrespondingly reduced.

It will be appreciated that the length of valve travel required for thevalve member 28 is considerably effected by the spacings of the variousfeed ports of which 37 are examples. If it is required to avoid thedrilling of complicated passages within the housing 10 then thearrangement according to the present invention in which adjacent rowsare interconnected by the passages 36 provides a considerably reducedaxial spacing of the various feed passages and therefore enables aconsiderable reduction in the required travel of the valve. Even if itis not required to have a variable number of rows in use theinterconnected arrangement could still have advantages, however, theadvantage of this system is more pronounced when there are a largenumber of rows and a large amount of variation in the number of rows isrequired.

As can be seen in FIG 2 the individual bores of adjacent rows areangularly staggered by half the angular spacing between adjacent boresso that each bore is in line with the space between two bores of thenext adjacent row. This enables the bores to be interdigitated to someextent and hence enables the axial length of the motor to beconsiderably reduced without weakening the cylinder housing 10.

This point is again illustrated by comparison of FIGS. 3 and 4 which aresections through adjacent rows of bores and pistons. It will be notedthat whereas the row in FIG 3 has a piston and cylinder at the top andbottom of the section, in the case of FIG 4 these positions correspondwith an inter bore spacing. This, therefore, enables the bores to beaxially spaced apart by a distance which would involve contiguity of thebores of adjacent rows were they not angularly staggered.

lclaim:

l. A radial piston type hydraulic motor comprising: a cylinder housing,at least two rows of cylinder bores in said housing, a central axiallyextending fluid flow and return passage positioned in said housing,interconnecting fluid passages communicating with said central passageand arranged to permit substantially simultaneous flow of fluid to andfrom cylinder bores of said at least two rows of bores, and a valvemember axially movable in said central passage and arranged to controlflow and return of fluid to the bores of said at least two rows ofbores.

2. An hydraulic motor as claimed in claim 13 and in which said rowscomprise axially spaced rows of equiangularly spaced apart bores, thebores of one row being angularly displaced with reference to the boresof an adjacent row by half the angular spacing of adjacent bores of eachrow.

3. An hydraulic motor as claimed in claim 2 and in which the axialspacing of the rows is such that the bores of adjacent rows are at leastpartly interdigitated.

4. An hydraulic motor as claimed in claim 1 and in which said valvemember is arranged to bring a variable number of said rows intooperation.

5. An hydraulic motor as claimed in claim 1 and comprising a sphericalpiston closely fitting in each said bore.

6. An hydraulic motor as claimed in claim 5 and in whicl' there is anannular member surrounding said housing and having on its inner surfacea plurality of cam tracks, each track being adapted to cooperate withthe pistons of one row of the bores to tend to produce relativerotational movement between the housing and the annular member.

7. An hydraulic motor as claimed in claim 6 and in which said housing isfixed and said annular member is arranged to rotate about the housing.

8. An hydraulic motor as claimed in claim 1 and in which said housing isformed to produce said interconnecting passages.

1. A radial piston type hydraulic motor comprising: a cylinder housing,at least two rows of cylinder bores in said housing, a central axiallyextending fluid flow and return passage positioned in said housing,interconnecting fluid passages communicating with said central passageand arranged to permit substantially simultaneous flow of fluid to andfrom cylinder bores of said at least two rows of bores, and a valvemember axially movable in said central passage and arranged to controlflow and return of fluid to the bores of said at least two rows ofbores.
 2. An hydraulic motor as claimed in claim 13 and in which saidrows comprise axially spaced rows of equiangularly spaced apart bores,the bores of one row being angularly displaced with reference to thebores of an adjacent row by half the angular spacing of adjacent boresof each row.
 3. An hydraulic motor as claimed in claim 2 and in whichthe axial spacing of the rows is such that the bores of adjacent rowsare at least partly interdigitated.
 4. An hydraulic motor as claimed inclaim 1 and in which said valve member is arranged to bring a variablenumber of said rows into operation.
 5. An hydraulic motor as claimed inclaim 1 and comprising a spherical piston closely fitting in each saidbore.
 6. An hydraulic motor as claimed in claim 5 and in which there isan annular member surrounding said housing and having on its innersurface a plurality of cam tracks, each track being adapted to cooperatewith the pistons of one row of the bores to tend to produce relativerotational movement between the housing and the annular member.
 7. Anhydraulic motor as claimed in claim 6 and in which said housing is fixedand said annular member is arranged to rotate about the housing.
 8. Anhydraulic motor as claimed in claim 1 and in which said housing isformed to produce said interconnecting passages.